Nonreciprocal circuit device having a casing comprising two members of different thicknesses

Abstract

A nonreciprocal circuit device includes a permanent magnet, a ferrite element to which a DC magnetic flux is applied by said permanent magnet, a plurality of center electrodes provided on the ferrite element, an upper casing member, and a lower casing member. The upper and lower casing members accommodate the permanent magnet, the ferrite element, and the center electrodes. The thickness of the lower casing member is set to the range between 50% and 100% of the thickness of the upper casing member. The upper and lower casing members are made of an iron-based metal.

What is claimed is:  
     
       1. A nonreciprocal circuit device comprising: 
       a permanent magnet;  
       a ferrite element to which a DC magnetic flux is applied by said permanent magnet;  
       a plurality of center electrodes provided on said ferrite element; and  
       a metal casing including a base material which is made of an iron-based metal and which accommodates said permanent magnet, said ferrite element, and said center electrodes,  
       wherein said metal casing comprises a first casing member and a second casing member, the first casing member and said permanent magnet are in magnetic contact with each other, and the base material of the second casing member has a thickness greater than 50% and substantially less than 100% of a thickness of the base material of the first casing member.  
     
     
       2. A nonreciprocal circuit device according to  claim 1 , wherein the second casing member comprises a pair of second casing sidewalls that oppose each other. 
     
     
       3. A nonreciprocal circuit device according to  claim 1 , wherein the second casing member comprises a first pair of second casing sidewalls that oppose each other, and a second pair of second casing sidewalls that oppose each other. 
     
     
       4. A nonreciprocal circuit device according to  claim 1 , wherein the first casing member comprises a pair of first casing sidewalls that oppose each other, and the second casing member comprises a pair of second casing sidewalls that oppose each other, the first casing sidewalls and the second casing sidewalls being overlapped and joined to each other. 
     
     
       5. A nonreciprocal circuit device according to  claim 4 , further comprising a resin casing member which is incorporated in said metal casing and which accommodates said ferrite element and said center electrodes, said resin casing member having contact-preventing portions provided between respective inner surfaces of the first and second casing sidewalls and a peripheral surface of said permanent magnet. 
     
     
       6. A nonreciprocal circuit device according to  claim 5 , wherein said resin casing member is insert-molded in said second casing member so as to integrally join the same. 
     
     
       7. A nonreciprocal circuit device according to  claim 5 , wherein said contact-preventing portions have upper surfaces which are extended to a location higher than a bottom surface of the magnet. 
     
     
       8. A nonreciprocal circuit device according to  claim 7 , wherein said contact-preventing portions cover substantially all of an inner surface of each first casing sidewall. 
     
     
       9. A nonreciprocal circuit device according to  claim 4 , wherein said second casing sidewalls overlap respective inner surfaces of the first casing sidewalls. 
     
     
       10. A nonreciprocal circuit device according to  claim 9 , further comprising a resin casing member which is incorporated in said metal casing and which accommodates said ferrite element and said center electrodes, said resin casing member having contact-preventing portions provided between respective inner surfaces of the first and second casing sidewalls and a peripheral surface of said permanent magnet. 
     
     
       11. A nonreciprocal circuit device according to  claim 10 , wherein said resin casing member is insert-molded in said second casing member so as to integrally join the same. 
     
     
       12. A nonreciprocal circuit device according to  claim 4 , wherein said second casing sidewalls overlap respective outer surfaces of the first casing sidewalls. 
     
     
       13. A nonreciprocal circuit device according to  claim 1 , wherein the first casing member and the second casing member are joined by welds. 
     
     
       14. A nonreciprocal circuit device according to  claim 1 , wherein at least one of the first casing member and the second casing member has plated surfaces comprising one of nickel and copper, and said plated surfaces are further plated with silver. 
     
     
       15. A nonreciprocal circuit device according to  claim 14 , wherein said plated surfaces consist essentially of nickel plated with silver. 
     
     
       16. A non reciprocal circuit device according to  claim 1 , wherein said DC magnetic flux is unsaturated in said second casing member. 
     
     
       17. A nonreciprocal circuit device according to  claim 1 , wherein said metal casing comprises cold rolled carbon steel. 
     
     
       18. A communication apparatus comprising at least one of a transmission circuit and a reception circuit, said circuit comprising the nonreciprocal circuit device according to  claim 1 . 
     
     
       19. A nonreciprocal circuit device comprising: 
       a permanent magnet;  
       a ferrite element to which a DC magnetic flux is applied by said permanent magnet;  
       a plurality of center electrodes provided on said ferrite element; and  
       a metal casing including a base material which is made of an iron-based metal and which accommodates said permanent magnet, said ferrite element, and said center electrodes,  
       wherein said metal casing comprises a first casing member and a second casing member, the first casing member and said permanent magnet are in magnetic contact with each other, and the base material of the second casing member as a thickness greater than 50% and substantially less than 100% of a thickness of the base material of the first casing member;  
       wherein the first casing member comprises a pair of first casing sidewalls that oppose each other, and the second casing member comprises a pair of second casing sidewalls that oppose each other, the first casing sidewalls and the second casing sidewalls being overlapped and joined to each other;  
       wherein a resin casing member is incorporated in said metal casing and accommodates said ferrite element and said center electrodes, said resin casing member having contact-preventing portions provided between respective inner surfaces of the first and second casing sidewalls and a peripheral surface of said permanent magnet; and  
       wherein said contact-preventing portions have a thickness greater than that of the upper casing member, and have upper surfaces which are extended to a location higher than a bottom surface of the magnet.  
     
     
       20. A nonreciprocal circuit device comprising: 
       a permanent magnet;  
       a ferrite element to which a DC magnetic flux is applied by said permanent magnet;  
       a plurality of center electrodes provided on said ferrite element; and  
       a metal casing including a base material which is made of an iron-based metal and which accommodates said permanent magnet, said ferrite element, and said center electrodes,  
       wherein said metal casing comprises a first casing member and a second casing member, the first casing member and said permanent magnet are in magnetic contact with each other, and the base material of the second casing member has a thickness greater than 50% and substantially less than 100% of a thickness of the base material of the first casing member;  
       wherein the first casing member comprises a pair of first casing sidewalls that oppose each other, and the second casing member comprises a pair of second casing sidewalls that oppose each other, the first casing sidewalls and the second casing sidewalls being overlapped and joined to each other;  
       wherein said second casing sidewalls overlap respective inner surfaces of the first casing sidewalls;  
       wherein a resin casing member is incorporated in said metal casing and accommodates said ferrite element and said center electrodes, said resin casing member having contact-preventing portions provided between respective inner surfaces of the first and second casing sidewalls and a peripheral surface of said permanent magnet;  
       wherein said contact-preventing portions have a thickness greater than that of the upper casing member, and have upper surfaces which are extended to a location higher than a bottom surface of the magnet.